A low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa for high-temperature enameling firing and its production method

Abstract

The present invention provides a low-carbon hot-rolled high-strength enamel steel with a yield strength of 360 MPa level and high temperature resistance for enameling, and its production method. The composition is as follows: C: 0.050% - 0.100%, Si: 0.010% - 0.030%, Mn: 0.350 - 0.550%, P ≤ 0.015%, S ≤ 0.010%, Al: 0.025 - 0.070%, N ≤ 0.010%, Ti: 0.020 - 0.070%, Nb: 0.010 - 0.050%, Mo: 0.050 - 0.190%, 2Ti + Nb = Mo, and the balance is Fe and inevitable inclusions. Compared with the prior art, for the composition and the supporting production method designed by the present invention, the yield strength of the product is 400 - 440 Mpa, the tensile strength can reach 500 Mpa, the elongation after fracture is > 20%, and the yield strength after enameling can be maintained at more than 85% of the yield strength before enameling.

Description

Technical Field

[0001] The present invention belongs to the technical field of enameled steel, and particularly relates to a low-carbon hot-rolled high-strength enameled steel with a yield strength of 360 MPa and high temperature resistance for enameling and a production method thereof. Background Art

[0002] The production processes of hot-rolled enameled products mainly include: steelmaking process, hot-rolling process, pickling process and enameling process. Among them, in the enameling process, the formed base blank is coated with porcelain enamel, and then enamel treatment is carried out at a temperature above 800 °C. The porcelain enamel coating can prevent the enameled steel plate from rusting, and can resist the erosion of various liquids. The excellent properties such as high hardness, high temperature resistance, wear resistance and insulation on the metal blank make the enameled products have a wider range of uses.

[0003] There are many types of enameled steel plates. According to the production process, they are divided into hot-rolled plates (i.e., pickled plates), cold-rolled plates and clad plates, etc.; and hot-rolled enameled steel plates (steel for Japanese enamel) are divided into different strength levels such as 300 MPa, 330 MPa and 360 MPa according to the yield strength. With the continuous improvement of the performance requirements for enameled steel plates, the upper limit of the strength of enameled steel is also increasing continuously. In particular, it is required that the steel plate still has a sufficiently high yield strength after being fired at high temperature twice, namely the primer firing and the topcoat firing, to meet the safety requirements for use as large structural parts.

[0004] The performance requirements for enameled steel plates mainly include strength, formability, weldability and anti-scaling explosion resistance. Among them, strength, formability and weldability are related to alloying elements, matrix structure and second-phase precipitates in the steel. And the scaling explosion problem of enameled products has always been one of the main problems affecting their quality. The hydrogen storage performance of the steel plate is the main link to control the occurrence of the scaling explosion phenomenon. The size of the hydrogen storage performance of the steel plate is affected by the number of hydrogen storage traps (grain boundaries, dislocation density and second-phase particles). The more hydrogen storage traps, the stronger the hydrogen storage capacity of the steel plate and the stronger the anti-scaling explosion performance.

[0005] In the existing design and application practices, most of the research focuses mainly on the formability and anti-scaling explosion resistance of the steel plate, and rarely involves the strength problem of the steel plate. The yield strength of most enameled steel plates is generally lower than 300 MPa before enameling. After being fired at a high temperature above 800 °C, the yield strength of the steel plate will decrease significantly, even lower than about 200 MPa.

[0006] In view of the above problems, some solutions have also been proposed in the prior art. For example, the patent with publication number CN 103540845 A, published on January 29, 2014, discloses a hot-rolled thin-sheet enameling steel with a yield strength of 330 MPa and its manufacturing method. The chemical composition by weight percentage is as follows: C: 0.02 - 0.07%, Si ≤ 0.05%, Mn: 0.10 - 0.50%, P ≤ 0.020%, S ≤ 0.010%, Ti: 0.04 - 0.10%, Als: 0.02 - 0.08%, N ≤ 0.008%, and the balance is Fe and other inevitable impurities. This patent adopts a low-carbon, Ti microalloy composition design and combines processes such as hot continuous rolling controlled rolling and controlled cooling to achieve a hot-rolled thin-sheet enameling steel with a yield strength of 330 MPa. However, it does not solve the problem of a significant decrease in yield strength after high-temperature enameling at temperatures above 800°C.

[0007] The patent with publication number CN 115522129 A, published on December 27, 2022, discloses a 330 MPa grade wide-width thin-gauge high-quality hot-rolled enameling steel and its production method. The chemical composition by weight percentage is C: 0.02 - 0.06%, Si: 0.05 - 0.1%, Mn: 0.5 - 0.9%, Ti: 0.03 - 0.08%, N: 0.003 - 0.008%, P ≤ 0.015%, S ≤ 0.008%, Mg: 0.001 - 0.004%, and the balance is Fe and inevitable impurities. The yield strength of this patent's hot-rolled enameling steel is ≥ 330 MPa, the tensile strength is ≥ 400 MPa, and the elongation is ≥ 40%. However, it also does not solve the problem of a significant decrease in yield strength after high-temperature enameling.

[0008] The main problems existing in the above prior art are as follows: In most of the component systems designed by the technology, although the yield strength of the mechanical properties of the hot-rolled sheet can reach above 330 MPa, the decrease in yield strength after high-temperature enameling is relatively large. This not only increases the cost but also makes it difficult to control the properties of the steel plate, and it is also greatly affected by the processing technology. Summary of the Invention

[0009] The purpose of the present invention is to provide a low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa that is resistant to high-temperature enameling and its production method. Through the design of the component system and its supporting production method, the overall performance of the produced steel plate is excellent and the performance after enameling is stable, solving the problem of a significant decrease in the mechanical properties of the steel plate after enameling.

[0010] The specific technical solution of the present invention is as follows:

[0011] A low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa that is resistant to high-temperature enameling, comprising the following components by mass percentage:

[0012] C: 0.050% - 0.100%, Si 0.010% - 0.030%, Mn: 0.350 - 0.550%, P ≤ 0.015%, S ≤ 0.010%, Al: 0.025 - 0.070%, N ≤ 0.010%, Ti: 0.020 - 0.070%, Nb: 0.010 - 0.050%, Mo: 0.050 - 0.190%, the balance being Fe and unavoidable inclusions.

[0013] The composition of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling firing also satisfies: 2Ti + Nb = Mo.

[0014] The hot-rolled microstructure of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling firing is polygonal ferrite and cementite precipitated at grain boundaries. The area ratio of polygonal ferrite to cementite is 4 ± 0.2:1, including acicular ferrite, and the average grain size is 18.5 ± 1 μm;

[0015] The yield strength of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling firing is 400 - 440 MPa, the tensile strength ≥ 500 MPa, and the elongation after fracture is greater than 20%;

[0016] After the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling firing is fired, the microstructure is polygonal ferrite and strip-shaped cementite, the average grain size is 20 ± 1 μm, and the area ratio of ferrite to cementite is 5 ± 0.2:1.

[0017] After the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling firing is fired, the yield strength ≥ 370 MPa, and the yield strength after firing can be maintained above 85% of the yield strength before firing.

[0018] A production method of a low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling firing provided by the present invention includes the following processes: steelmaking process, hot-rolling process, and pickling process;

[0019] In the steelmaking process, the above composition system is smelted and cast into slab;

[0020] In the hot-rolling process, the slab is heated and held, hot-rolled, laminar cooled, and coiled to obtain a hot-rolled sheet;

[0021] In the hot-rolling, the hot-rolling holding temperature is 1200 ± 20 °C, the holding time is 2 ± 0.2 h, the starting rolling temperature: 1000 - 1100 °C, the finishing rolling temperature: 900 - 950 °C;

[0022] The coiling is carried out after the finish rolling. The steel is cooled to the coiling temperature through laminar cooling, and the cooling rate is controlled at 20 - 30 °C / s. The coiling temperature is 600 - 680 °C.

[0023] In the pickling process, the hot-rolled sheet is pickled with a dilute hydrochloric acid solution with a mass concentration of 8% - 10%, and the temperature of the pickling solution is controlled at 60 - 70 °C.

[0024] Compared with the prior art, the composition system and production method of the hot-rolled high-strength enameling steel designed by the present invention have a simple process flow, and the product performance is stable and controllable. The yield strength of the mechanical properties of the hot-rolled steel plate can reach 400 - 440 MPa, the tensile strength can reach more than 500 MPa, and the elongation after fracture is greater than 20%. After enameling, the yield strength of the steel plate is stable above 370 MPa, the anti-scaling explosion performance is good, and the mechanical properties before and after enameling are stable. Description of the Drawings

[0025] Figure 1 It is the hot-rolled structure of Example 1, which is mainly composed of polygonal ferrite and a small amount of short strip-shaped cementite precipitated along the grain boundaries. Some of the ferrite is needle-shaped, the grain size is about 18 μm, and the area ratio of ferrite to cementite is 4:1.

[0026] Figure 2 It is the structure after enameling of Example 1, which is mainly composed of polygonal ferrite and a small amount of long strip-shaped cementite precipitated along the grain boundaries. The grain size is about 19 μm, and the area ratio of ferrite to cementite is 5:1.

[0027] Figure 3 It is the hot-rolled structure of Example 2, which is mainly composed of polygonal ferrite and short strip-shaped cementite precipitated along the grain boundaries. Some of the ferrite is needle-shaped, the grain size is about 19 μm, and the area ratio of ferrite to cementite is 4.2:1.

[0028] Figure 4 It is the structure after enameling of Example 2, which is mainly composed of polygonal ferrite and long strip-shaped cementite precipitated along the grain boundaries. The grain size is about 20 μm, and the area ratio of ferrite to cementite is 5:1.

[0029] Figure 5 It is the hot-rolled structure of Comparative Example 1, which is mainly composed of polygonal ferrite and a small amount of pearlite. The grain size is about 20 μm, and the area ratio of ferrite to cementite is 7:1.

[0030] Figure 6 It is the structure after enameling of Comparative Example 1, which is mainly composed of polygonal ferrite and long strip-shaped cementite precipitated along the grain boundaries. The grain size is about 22 μm, The area ratio of ferrite to cementite is 5:1. Detailed Embodiments

[0031] A low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa and high temperature resistance to enameling firing, comprising the following components by mass percentage:

[0032] C: 0.050% - 0.100%, Si 0.010% - 0.030%, Mn: 0.350 - 0.550%, P ≤ 0.015%, S ≤ 0.010%, Al: 0.025 - 0.070%, N ≤ 0.010%, Ti: 0.020 - 0.070%, Nb: 0.010 - 0.050%, Mo: 0.050 - 0.190%, and the balance is Fe and inevitable inclusions.

[0033] The composition of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa and high temperature resistance to enameling firing also satisfies: 2Ti + Nb = Mo.

[0034] The design idea of this application is as follows:

[0035] Carbon (C): C determines the strength, plasticity and formability of the steel plate. The lower the C content, the lower the strength of the steel plate, especially the strength after high-temperature enameling firing is lower, but the formability is better; the higher the C content, the strength increases but it is not conducive to weldability and formability. In order to obtain a lower r value, good isotropy, and taking into account weldability and formability, the C content of the present invention is controlled to be 0.050 - 0.100%. Most of the carbon will precipitate in the form of carbides in the austenite stage, and the precipitated carbide particles greatly improve the yield strength of the steel plate.

[0036] Silicon (Si): Si exists as a residual element in the steel. If its content is too high, it will damage the enamel adhesion. Therefore, in the present invention, the Si content is controlled ≤ 0.03%.

[0037] Manganese (Mn): Mn is not only a deoxidizer and desulfurizer in the steel, forming MnS precipitation with S to prevent the formation of FeS and causing corner cracks in the continuous casting billet, but also a solid solution strengthening element, which can increase strength and reduce the r value, but too high will reduce the plasticity of the steel. Therefore, the Mn content of the present invention is 0.350 - 0.550%.

[0038] Phosphorus (P): P is a harmful element in the steel, which is easy to segregate at the grain boundaries and affect the enamel quality. Therefore, P is controlled ≤ 0.015%.

[0039] Sulfur (S): S is an impurity element in the steel and mainly exists in the form of MnS. In enameling steel, sulfides show beneficial effects within a certain range. By adding elements such as Ti and Nb, composite inclusions such as TiS and Ti4C2S2 can be formed. Such inclusions are mostly spherical, which can reduce the damage to plasticity, and can also be used as hydrogen storage traps to improve the anti-scaling explosion performance. At the same time, with the increase of sulfur, the fatigue performance can also be improved. The range of the S content of the present invention is controlled at S ≤ 0.010%.

[0040] Aluminum (Al): In aluminum-killed steel, Al is not only a strong deoxidizing element but also plays a role in refining the grain size. In addition, Al reacts with N to form AlN, and AlN plays a certain role in improving the anti-scaling explosion performance of the steel. In the present invention, the Al content is 0.025 - 0.070%.

[0041] Titanium (Ti): Ti plays a role in fixing nitrogen, hindering recrystallization, and obtaining fine grains in the steel. Ti generally forms second-phase precipitates such as TiC, TiN, TiS, Ti(C,N), and Ti4C2S2 with C and N. The binding energy of these precipitates with hydrogen atoms is relatively large, which can be used as irreversible traps to fully fix hydrogen atoms near the precipitate particles, reduce the occurrence of scaling explosion phenomenon, and at the same time can also inhibit the precipitation of large-sized MnS, improving the fatigue performance and formability of the steel plate. In the present invention, the Ti content is 0.020 - 0.070%.

[0042] Niobium (Nb): The addition of Nb can not only effectively prevent the recrystallization of deformed austenite, making the rolling interval the non-recrystallized interval, but also promote deformation-induced precipitation, forming nano-scale precipitation phase NbC during the coiling process, which greatly improves the strength of the steel. In the present invention, the Nb content is 0.010 - 0.050%.

[0043] Molybdenum (Mo): Mo is added to the steel as a strengthening functional element. It can not only promote the precipitation of carbides such as TiC and NbC in enameling steel, but also form (Ti,Nb,Mo)C with (Ti,Nb)C, which can inhibit the coarsening behavior of particles during high-temperature and isothermal processes, significantly reduce the size of the precipitation phase in Ti and Nb steels, and effectively inhibit coarsening. If the Mo content is too low, it will not play a key role, and because the price of Mo element is expensive, so in the present invention, the range of Mo is controlled to be 0.050 - 0.190%.

[0044] In the present invention, by adding three key alloying elements Ti, Nb, and Mo to the steel, the grains of the steel are significantly refined, and the alloying elements are mostly evenly dispersed in the form of carbides. The effects of fine grain strengthening, second-phase strengthening, and solid solution strengthening of the steel are significantly improved, so that the mechanical properties of the steel are significantly optimized. The yield strength can reach 438 MPa, the tensile strength reaches 500 MPa, and the elongation after fracture is greater than 20%.

[0045] In addition, since the steel contains Mo and the weight percentage relationship is 2Ti + Nb = Mo, research has found that under this element ratio, the Mo element can maximize its functionality. Moreover, the Mo-containing carbides precipitated from the matrix, such as composite carbide particles like MoC and (Ti,Mo)C, (Ti,Nb,Mo)C, etc., have a small growth tendency during high-temperature annealing and can inhibit the coarsening of Ti- or Nb-containing carbides, enabling the steel to maintain excellent mechanical properties after long-term high-temperature annealing and reducing the loss of properties after annealing and high-temperature enameling.

[0046] The production method of a low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade for high-temperature enameling provided by the present invention includes the following processes: steelmaking process, hot-rolling process, and pickling process;

[0047] The specific process control is as follows:

[0048] 1) Smelting process: Smelting is carried out according to the designed chemical composition above. During the refining process, ferrosulfur, sponge titanium, etc. are added for alloying treatment, and then it is cast into a slab;

[0049] 2) Hot-rolling process: The cast billet is heated, descaled, hot-rolled, and coiled after laminar cooling to obtain a hot-rolled coil. Among them, the rough rolling starting temperature is 1000 - 1100 °C, the finishing rolling temperature is 900 - 950 °C, the cooling rate is controlled at 20 - 30 °C / s, and the coiling temperature is 600 - 680 °C. After finishing rolling, it is cooled to the coiling temperature through laminar cooling. Since rapid cooling in production increases the supercooling degree and the nucleation driving force is large, the ferrite grains are fine and some are needle-shaped, with an average grain size of 18.5 ± 1 μm; the cementite is mostly in short strip or granular form, and the area ratio of ferrite to cementite is 4 ± 0.2:1. After high-temperature enameling, the needle-shaped ferrite in this hot-rolled structure basically disappears, and the enameling structure is composed of polygonal ferrite and long strip cementite, with an average grain size of about 20 ± 1 μm, and the area ratio of ferrite to cementite is about 5 ± 0.2:1. After high-temperature enameling, the grain size changes little, and the fine grain strengthening effect decreases insignificantly; part of the cementite dissolves back, and solid solution strengthening and precipitation strengthening play a dominant role, and the strength is still at a relatively high level after high-temperature enameling.

[0050] 3) Acid rolling process: Pickling is carried out using a dilute hydrochloric acid solution with a mass concentration of 8% - 10%, and the pickling solution temperature is controlled at 60 - 70 °C.

[0051] The production process used in the present invention, such as the starting rolling temperature, finishing rolling temperature, and controlled cooling after finishing rolling in the hot-rolling process, can not only fully embody the advantages of the chemical composition designed in the present invention, that is, give full play to the synergistic promotion effect of the three alloying elements Ti, Nb, and Mo, making the matrix grain size and the second-phase precipitation particle size fine and the coarsening degree small after high-temperature enameling; but also the process flow is simple, the production quality is high, and the product performance is excellent and stable and controllable.

[0052] The yield strength of the heat-resistant enameling low-carbon hot-rolled high-strength enameling steel produced is 400 - 440 MPa, the tensile strength is ≥500 MPa, and the elongation after fracture is greater than 20%; the yield strength of the heat-resistant enameling low-carbon hot-rolled high-strength enameling steel after enameling is ≥380 MPa.

[0053] The following is a description in combination with the following specific embodiments.

[0054] Example 1

[0055] A heat-resistant enameling low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa grade, including the following components by mass percentage: As shown in Table 1, the balance not shown in Table 1 is Fe and inevitable impurities.

[0056] Table 1 Steel compositions of each example

[0057]

[0058] The production method of the heat-resistant enameling low-carbon hot-rolled high-strength enameling steel described in Example 1 includes the following steps:

[0059] 1) Smelting process: Smelt according to the designed chemical composition above, add ferrosulfur, sponge titanium, etc. in the refining process for alloying treatment, and then cast into slab billets;

[0060] 2) Hot rolling process: Heat the cast billets, remove phosphorus, hot roll, laminar flow cool, and coiling to obtain hot-rolled sheets. Among them, the hot rolling holding temperature is 1200 °C, the holding time is 2 h, the rough rolling starting temperature is controlled at 1100 °C, the finish rolling temperature is controlled at: 900 °C, through laminar flow cooling, the cooling rate is controlled at 25 °C / s, cooled to the coiling temperature, and the coiling temperature is set at: 620 °C;

[0061] 3) Pickling process: Put the hot-rolled sheets into 10% dilute hydrochloric acid for pickling, and the pickling temperature is 70 °C;

[0062] 4) Simulated enameling process: Heat the hot-rolled and pickled steel sheets at high temperature for enameling, the enameling temperature is 855 °C, and the enameling time is 10 minutes.

[0063] Test the mechanical properties of the enameling steel produced in Example 1 before and after enameling according to GB / T 228.1-2021 Metallic materials - Tensile testing method, and at the same time test the anti-scaling explosion performance. The test results are shown in Table 2.

[0064] Table 2 Mechanical properties and anti-scaling explosion performance of the enameling steel in Example 1 before and after enameling

[0065]

[0066] Example 2

[0067] A low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa and high temperature resistance to enameling firing, comprising the following components by mass percentage: as shown in Table 1 (the same as the components in Example 1), the balance not shown in Table 1 is Fe and unavoidable impurities.

[0068] The production method of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa and high temperature resistance to enameling firing described in Example 2, comprising the following steps:

[0069] 1) Smelting process: Smelt according to the designed chemical composition above, add ferrosulfur, titanium sponge, etc. in the refining process for alloying treatment, and then cast into slabs;

[0070] 2) Hot rolling process: Obtain hot-rolled sheets after heating, descaling, hot rolling and laminar cooling of the cast slabs, wherein the hot rolling holding temperature is 1200 °C, the holding time is 2 h, the starting rolling temperature of finish rolling is controlled at 1100 °C, the final rolling temperature is controlled at: 920 °C, cool to the coiling temperature through laminar cooling, the cooling rate is controlled at 30 °C / s, cool to the coiling temperature, and the coiling temperature is set at: 660 °C;

[0071] 3) Pickling process: Put the hot-rolled sheets into 10% dilute hydrochloric acid for pickling, and the pickling temperature is 70 °C;

[0072] 4) Enameling firing process: Perform high-temperature enameling firing on the hot-rolled and pickled steel sheets, the enameling firing temperature is 855 °C, and the enameling firing time is 10 minutes.

[0073] Test the mechanical properties and anti-scaling explosion properties of the enameling steel produced in Example 2 before and after enameling firing, and the test results are shown in Table 3.

[0074] Table 3 Mechanical properties and anti-scaling explosion properties of the enameling steel in Example 2 before and after enameling firing

[0075]

[0076] Comparative Example 1

[0077] A comparative example of a low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa and high temperature resistance to enameling firing, comprising the following components by mass percentage: as shown in Table 4, the balance not shown in Table 4 is Fe and unavoidable impurities.

[0078] Table 4 Steel composition of Comparative Example 1

[0079] element C Si Mn P S Al Ti Nb Mo N Content (%) 0.065 0.03 0.36 ≤0.015 ≤0.010 0.04 0.02 0.03 0.015 ≤0.010

[0080] The production method of the comparative example, comprising the following steps:

[0081] 1) Smelting process: Smelt according to the designed chemical composition above. Add ferrosulfur, titanium sponge, etc. during the refining process for alloying treatment, and then cast into slab billets;

[0082] 2) Hot rolling process: Obtain hot rolled sheets after heating, descaling, hot rolling and laminar cooling of the cast billets. Among them, the hot rolling holding temperature is 1200 °C, the holding time is 2 h, the starting rolling temperature of finish rolling is controlled at 1100 °C, the final rolling temperature is controlled at 900 °C, cooled to the coiling temperature through laminar cooling, the cooling rate is controlled at 20 °C / s, cooled to the coiling temperature, and the coiling temperature is set at: 620 °C;

[0083] 3) Pickling process: Put the hot rolled sheets into 10% dilute hydrochloric acid for pickling, and the pickling temperature is 70 °C;

[0084] 4) Glazing process: Perform high-temperature glazing on the hot rolled and pickled steel sheets. The glazing temperature is 855 °C and the glazing time is 10 minutes.

[0085] The mechanical properties and anti-scaling explosion properties of the enameled steel produced in Comparative Example 1 before and after glazing were tested, and the test results are shown in Table 3.

[0086] Table 5 Mechanical properties and anti-scaling explosion properties of the enameled steel in Comparative Example 1 before and after glazing

[0087]

[0088] The underlined data above are the data that do not meet the requirements of the present invention.

[0089] In the above-mentioned Example 1 and Example 2, the main difference is that the coiling temperatures of Example 1 and Example 2 are controlled at 620 °C and 660 °C respectively. Hot rolled steel sheets with higher yield strength are obtained under this composition system, and the mechanical properties of the steel sheets still remain at a relatively high level after high-temperature glazing. In the comparative example, due to the content of Mo element not meeting the formula 2Ti + Nb = Mo, under the same processing technology, the strength after glazing decreases significantly. To sum up, the composition system adopted in this example shows excellent mechanical properties in the designed processing scheme and has high performance stability after high-temperature glazing.

[0090] The above specific embodiments are only the best examples and are not restrictive implementations of the technical solutions of the present invention.

Claims

1. A low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa and high temperature resistance for enameling firing, characterized in that, The low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa for high-temperature enameling firing comprises the following components by mass percentage: C: 0.050% - 0.100%, Si 0.010% - 0.030%, Mn: 0.350 - 0.550%, P ≤ 0.015%, S ≤ 0.010%, Al: 0.025 - 0.070%, N ≤ 0.010%, Ti: 0.020 - 0.070%, Nb: 0.010 - 0.050%, Mo: 0.050 - 0.190%, and the balance is Fe and inevitable inclusions; The components of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa for high-temperature enameling firing also satisfy: 2Ti + Nb = Mo; The hot-rolled microstructure of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa for high-temperature enameling firing is polygonal ferrite, acicular ferrite, and cementite precipitated at grain boundaries. The area ratio of polygonal ferrite to cementite is 4 ± 0.2:1, and the average grain size is 18.5 ± 2 μm. The yield strength of the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa for high-temperature enameling firing is 400 - 440 MPa, the tensile strength ≥ 500 MPa, and the elongation after fracture is greater than 20%; After the low-carbon hot-rolled high-strength enameling steel with a yield strength of 360 MPa for high-temperature enameling firing is fired, the microstructure is polygonal ferrite and strip-shaped cementite, the average grain size is 20 ± 1 μm, and the area ratio of ferrite to cementite is 5 ± 0.2:1; the yield strength ≥ 370 MPa, and the yield strength after firing can remain above 85% of the yield strength before firing.

2. A production method of a low-carbon hot-rolled high-strength enamel steel with a yield strength of 360 MPa for high-temperature enameling as described in claim 1, characterized in that, The production method comprises the following processes: Steelmaking process, hot-rolling process, and pickling process.

3. The production method according to claim 2, characterized in that, In the hot-rolling process, a hot-rolled sheet is obtained after heating and holding, hot-rolling, laminar cooling, and coiling of the slab.

4. The production method according to claim 3, characterized in that, For the hot-rolling, the hot-rolling starting temperature: 1000 - 1100 °C, the finishing rolling temperature: 900 - 950 °C.

5. The production method according to claim 3, characterized in that, For the laminar cooling, the cooling rate is controlled at 20 - 30 °C / s.

6. The production method according to claim 3, characterized in that, For the coiling, the coiling temperature: 600 - 680 °C.

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